That is astonishingly unusable to me. I'm shocked. I never had anything so dismal with 56 or 54 series. To me, that would be a defective flash.

Yep, but it is what it is... you cant modify it and nobody can fully explain it.. other than the sensor being a bit too sensitive so it will vary in different conditions (hot environment, warming batteries, quicker recharges [with ext power packs] lens hoods and diffusers etc) but that doesnt provide any help to the problem.

It is a lot better on anything less than full power and I have done full on fashion shoots at closer range with no problems, but I have done distant 'stage' shoots that cause the overheating, which is why i now have both the 58 and 60 and I just swap them over.